Flip-flops are common building blocks in synchronous systems, and are typically implemented using conventional static complementary metal oxide semiconductor (CMOS) logic, which generates pattern dependent switching current. When used in analog circuits, such as analog to digital converters (ADCs), or in time domain signal processing, the pattern dependent switching current may contaminate analog signals through either the supply network or by substrate coupling, and may also contribute to heating device circuitry. Moreover, pattern dependent switching current may render secure devices, such as smart cards and cryptographic processors, vulnerable because the secret keys of the secure devices may be revealed by correlation to device power consumption through differential power analysis (DPA). There is thus a need to provide flip-flops that do not produce pattern dependent switching currents.